1. Field of the Invention
This invention relates to a process for producing titanium carbonitride.
2. Description of the Prior Art
Titanium carbide (TiC)-base sintered alloys, which are generally produced by sintering titanium carbide together with molybdenum carbide (Mo.sub.2 C) or other carbides by using a nickel binder, have heretofore been used as high speed, light cutting tools. However, titanium carbide-base alloys are not suitable for high speed, heavy cutting tools and interrupted cutting tools because of their brittleness.
Recently, it has been proposed to use titanium carbonitride instead of titanium carbide as a base material for sintered alloys. Titanium carbonitride provides sintered alloys exhibiting enhanced toughness and transverse rupture as compared with conventional titanium carbide-base sintered alloys. The titanium carbonitride-base sintered alloys can be used as high speed, heavy cutting tools and interrupted cutting tools, i.e., widely used in cutting tool applications. Furthermore, titanium carbonitride exhibits enhanced thermal resistance and toughness, and consequently, the use thereof is expanding steadily in the fields of, for example, sintered hard metals and heat resisting alloys. For most applicantions of titanium carbonitride, titanium carbonitride of a high purity and of a fine powder form is desired.
Conventionally, titanium carbonitride is produced by a method wherein a uniform mixture of the predetermined proportion (i.e., corresponding to the intended titanium carbonitride composition TiCmNn) of a finely divided titanium carbide (TiC) and a finely divided titanium nitride (TiN) is compression molded, and then, the molded product is heated in a nitrogen atmosphere maintained at approximately 1,500.degree. C., and finally, the product is pulverized, by using, for example, a ball mill, into a finely divided particle form. This conventional method is not advantageous for the following reasons. First, it is difficult to pulverize a sintered product of the obtained titanium carbonitride into a size of approximately one micron, and moreover, it cannot be avoided that, during the course of pulverization, foreign matters are incorporated into the sintered product and the sintered product is oxidized. Secondly, the sintered product is not always a homogeneous solid solution.